[The effect of local anesthetics on the isolated human right atrial appendages--1: A comparison of inhibition of contractility with bupivacaine and lidocaine].

The inhibition of cardiac muscle contractility with bupivacaine was about tenfold of that with lidocaine, namely the ID50 values of bupivacaine and lidocaine were 10(-6) M and 10(-5) M, respectively. With bupivacaine above 3 x 10(-6) M, the contraction was diminished completely. In the medium of a high calcium concentration (Ca2+:5.0 mM), the effect of lidocaine (10(-5) M) was antagonized markedly, but that of bupivacaine was not antagonized so much. These results suggest that they might have some different mechanisms in respect to the inhibition of the contractility, for instance bupivacaine affecting mainly sarcoplasmic reticulum and lidocaine affecting mainly sarcolemma.